Represent fingerprint internally as byte array

broker/broker.go

@@ -143,7 +143,7 @@ func (ctx *BrokerContext) AddSnowflake(id string, proxyType string, natType stri
 type ClientOffer struct {
 	natType     string
 	sdp         []byte
-	fingerprint string
+	fingerprint [20]byte
 }
 
 func main() {

broker/ipc.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"container/heap"
+	"encoding/hex"
 	"fmt"
 	"log"
 	"net"
@@ -130,11 +131,16 @@ func (i *IPC) ClientOffers(arg messages.Arg, response *[]byte) error {
 	}
 
 	offer := &ClientOffer{
-		natType:     req.NAT,
-		sdp:         []byte(req.Offer),
-		fingerprint: req.Fingerprint,
+		natType: req.NAT,
+		sdp:     []byte(req.Offer),
 	}
 
+	fingerprint, err := hex.DecodeString(req.Fingerprint)
+	if err != nil {
+		return sendClientResponse(&messages.ClientPollResponse{Error: err.Error()}, response)
+	}
+	copy(offer.fingerprint[:], fingerprint)
+
 	// Only hand out known restricted snowflakes to unrestricted clients
 	var snowflakeHeap *SnowflakeHeap
 	if offer.natType == NATUnrestricted {

common/messages/client.go

@@ -5,6 +5,7 @@ package messages
 
 import (
 	"bytes"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 
@@ -105,6 +106,9 @@ func DecodeClientPollRequest(data []byte) (*ClientPollRequest, error) {
 	if message.Fingerprint == "" {
 		message.Fingerprint = defaultBridgeFingerprint
 	}
+	if hex.DecodedLen(len(message.Fingerprint)) != 20 {
+		return nil, fmt.Errorf("cannot decode fingerprint")
+	}
 
 	switch message.NAT {
 	case "":

common/messages/messages_test.go

@@ -344,6 +344,12 @@ func TestEncodeClientPollRequests(t *testing.T) {
 				defaultBridgeFingerprint,
 				nil,
 			},
+			{
+				"unknown",
+				"fake",
+				"123123",
+				fmt.Errorf(""),
+			},
 		} {
 			req1 := &ClientPollRequest{
 				NAT:         test.natType,